Rose extracts may help canned strawberries stay red for longer

An extract from rose petals may promote the retention of pigments in canned strawberries, even after processing, says new research.

Small concentrations of the rose ‘co-pigments’ significantly increased the lifetime of the anthocyanin compounds in strawberries responsible for the fruit’s characteristic colour, according to results published in the Journal of Agricultural and Food Chemistry​.

“The results presented here demonstrate that the addition of colourless rose petal polyphenols acting as co-pigments significantly reduces the thermal degradation of strawberry anthocyanins in model solutions, thus bringing about enhanced colour stability, even at a molar pigment/co-pigment ratio of 1:2,”​ wrote lead author Vasil Shikov from Hohenheim University in Stuttgart.

“In contrast to the addition of rosemary and thyme extracts, which have been used as anthocyanin-stabilizing agents at a 1:100 c-opigmentation ratio, rose petal polyphenols are effective at much lower concentrations, thus allowing an economically viable stabilization method,”​ added Shikov.

The research is very timely given recent concerns over the use of synthetic colourants in food, including canned strawberries. The recent Southamptom study reported that consumption of mixtures of additives including sunset yellow (E110), tartrazine (E102), carmoisine (E122), ponceau 4R (E124), allura red (E129) and sodium benzoate led to increased hyperactivity in children.

Strawberry products have commonly contained synthetic colourants such as ponceau 4R in order to enhance the colour of the product.

“Therefore, the substitution of synthetic food colorants by their natural counterparts and the development of methods to stabilize natural pigments are of utmost importance to meet consumer demands for safer and healthier food,”​ said Shikov and co-workers.

Study details​

Shikov and co-workers used the rose petal extracts as co-pigments in a model strawberry system. The stability of purified strawberry anthocyanins was tested after thermal processing at 85 degrees Celsius.

The researchers report that the time taken for half of the pigment to degrade, the so-called half-life, was significantly increased after adding the rose (Rosa​ damascena​ Mill.) petal extracts. Indeed, at a ratio of 1:2 pigment/co-pigment ratio the half-life was increased by 27 per cent, said the researchers.

The Stuttgart-based researchers also compared the stabilising effects of the rose petal extracts with other co-pigments, like kaempferol and quercetin.

Using a ratio of 1:2 the best results were observed by the rose petal extracts (27 per cent half-life increase), compared to 19 and 15 per cent for kaempferol and quercetin, respectively.

“The results obtained demonstrate that the addition of rose petal polyphenols slows the thermal degradation of strawberry anthocyanins, thus resulting in improved colour retention without affecting the gustatory quality of the product,”​ concluded the researchers.

Despite these promising results in the model system, the researchers added that a understanding is needed into the “interactions of both pigments and co-pigments with matrix compounds such as cell wall material, which may affect the efficiency of rose petal polyphenols in a complex food system”.​